Influence of trans-1,3,3,3-Tetrafluoropropene on the Structure-Properties Relationship of VDF- and TrFE-Based Terpolymers

trans-1,3,3,3-Tetrafluoropropene (1234ze) was copolymerized under free radical conditions with vinylidene fluoride (VDF) and trifluoroethylene (TrFE), for the first time, leading to statistical poly(VDF-ter-TrFE-ter-1234ze) electroactive terpolymers. The reactivity ratios of the three comonomer couples were determined (r(VDF) = 0.77; r(TrFE) = 0.32), (r(VDF) = 1.67; r(1234ze) = 0.00), and (gamma(TrFE) = 7.56; r(1234ze) = 0.00), at 48 degrees C, using the nonlinear fitting Mayo-Lewis method. 1234ze was shown to be regularly incorporated in the terpolymer chains over the entire course of the reaction providing terpolymer chains with statistical monomer distribution and almost constant composition. These new VDF/TrFE-based terpolymers were characterized by H-1 and F-19 liquid state NMR spectroscopy. The characteristic NMR signals of the VDF-1234ze dyads were identified by comparing the NMR spectral signatures of a poly(VDF82-co-1234ze(18)) copolymer and of a terpolymer. The thermal and electroactive properties of poly(VDF-ter-TrFE-ter-1234ze) terpolymers, with 1234ze content ranging from 0 to 6 mol % and molar masses above 55 kg/mol, were assessed. The randomly distributed 1234ze termonomer units induced the decreases of both the Curie and the melting temperatures of the terpolymer even at ltermonomer content (T-Curie = 70 degrees C and T-m = 126 degrees C and T-Curie = 72 degrees C and T-m = 150 degrees C; for a poly(VDF69-ter-TrFE28-ter-1234ze(3)) terpolymer and a poly(VDF65-co-TrFE35) copolymer, respectively). Films of the terpolymers were cast, and their electroactive properties were examined by D-E loops measurements. They showed that the presence of 1234ze decreased the remnant polarization (P-r = 45 mC/m(2) for a poly(VDF65-co-TrFE35) copolymer to 28 mC/m2 for a poly(VDF69-ter-TrFE25-ter-1234ze(6)) terpolymer) probably because it also decreased the crystallinity of the terpolymer. The combination of the studies of the reactivity of the monomers, of the terpolymer microstructures, and of the assessment of their physical properties provides insights into their structure property relationship.